The present invention relates generally to a prosthesis for the distal radio-ulnar joint and more particularly to a prosthesis for the restoration of pain free rotation of the forearm and stability of the ulna and wrist.
The ulnar head is an integral portion of the distal radio-ulnar joint (DRUJ). The DRUJ is essential for stable forearm rotation and the ulnar head serves as the fixed fulcrum at which the radius sigmoid notch articulates. The radius of curvature of the sigmoid notch is approximately twice that of the ulnar head and the motion between the two surfaces can be accurately described as rolling and sliding.
Disorders of the distal radio-ulnar joint are common and usually associated with pain, weakness, instability and loss of forearm rotation. Any loss of congruity between the sigmoid fossa of the radius and the ulnar head will result in painful loss of forearm rotation. Causes include congenital abnormalities such as Madelung's deformity, radial fractures, inflammatory arthritis and tears of the triangular fibro-cartilage complex. Furthermore, trauma may result in acute dislocation of the distal radio-ulnar joint itself, often in association with radial head fracture and tear of the interosseous membrane. Finally, many patients suffer from painful instability following previous surgical procedures on the distal radio-ulnar joint.
It is important to restore the ulnar head if an individual is to achieve stable and pain free forearm rotation in cases of DJD, inflammatory arthritis, or post traumatic arthritis of the ulnar head. The current salvage procedures without a prosthetic implant include, Darrach resection, hemi-resection, and suave-kapandji; however, all the surgical techniques render the distal ulna unstable leading to recurrence of pain, instability, and weakness.
Although any of the above procedures may produce reasonable results if correctly carried out and in appropriate patients, there are, however, many patients who are discontented with the results of surgery and who are seeking a suitable revision procedure to restore stability and pain free rotation at the distal radio-ulnar joint.